Thread: A Saturday at the backyard foundry

Hi Nick,
Thanks for your comments, I'd come to the same conclusions as far as pre heat... though I didn't know of the CO issues(do you happen to know if they apply to propane burners?)

Originally Posted by 4-6-4

I used a space age stuff called ( damn I can,t remember the name,)

ISOLITE ISOWOOL? Hope so because I've bought a box as I collect bits and pieces for my furnace.

Stuart

though I didn't know of the CO issues(do you happen to know if they apply to propane burners?)

I *think* that's the same.
We had been discussing about a heat-exchanger in the exhaust. But I was warned by someone who was a service man at Voest Alpine (I think), doing steel mills setups abroad and getting them to run. CO is a big issue with burners/furnaces. They frighten it a lot, it is constantly monitored. So I kept away from that idea.
Also, the oil is cheap enough.

The furnace liner is 3 cm of refractory concrete (1700°C) and at the outside a layer of 3 cm ceramic fibers. I made the observation, that the concrete helps in combustion with oil. As it helps to evaporate it more quickly. At full throttle, it is glowing orange. Above 500° C, you get spontaneous ignition of the oil (depending of what oil it is, but 500 is the upper limit). Diesel fuel is 280° C IIRC.

cant wait for swmbo to leave so I can set myself up like you Nick

but I love her and i guess she will never go ...not while i love her anyway

wow...great video

have a beer for me at the next Giessen und Grillen

Originally Posted by 4-6-4

I did all my iron at the RMIT Foundry School. I am only too glad to help the amateur. Yours 4-6-4

Oooh! A local type person. Do you still do metal casting?

Thanks Nick,
Based on what you've said I'm now thinking about a spiral of steel tube above the furnace exhaust. I can see three problems as I haven't bothered with the math yet. I am likely over guessing(I cant even use the word estimating) the amount of heat the will flow though the pipe wall, under guessing that amount of air flowing through the pipe and have no idea how long the pipe would last.

I can get oil "cheap" also....maybe a hybrid burner............. or maybe I should stop thinking so much and start building?

Do you coat the inside of you steel "melting pot"(the word escapes me atm) with anything?

Stuart

Well, the heat regenerator at the exhaust side:
It is very attractive from the energy POV. You have about 80% of the energy going out there. And it is completely wasted.
You have two advantages from hot air on the intake:
Less losses by heating up the air from 20° C to say 1500° C. And the flame will burn faster. The later is an advantage when burning oil, as the flame gets quite long.
I do have a 60 mm tube on the intake.
I you wind a spiral that takes heat from the exhaust, you'll have to find a practical setup that you quickly can remove to have access to the crucible. (A quick reminder: I broke the lid on my furnace, normally I do have one). That sprial has to be long enough to have enough time for the heat to be transferred to the intake air. I didn't calculate the length. Also, you have to consider what type of blower you use. Maybe it won't work with hot air.
The setup of ArtfulBudger where he takes of a bit of hot air from the combustion chamber to heat up the intake air doesn't work. The contact time is way too short. It was something around 2 ms. Roughly, it takes 1 m^3 of air for every liter of fuel you burn. And every liter of fuel has around 10 kWh. With that, you can calculate the air speed in the intake and thus the contact time. ArtfulBudger's setup only helps in pre-heating the oil (that's an advantage, I'll implement that too).
I wouldn't worry too much of the heat on the heat exchanger being too high. The air rushing through really cools it down. With my setup, that are 200 kg of air per hour!

I can get oil "cheap" also....maybe a hybrid burner............. or maybe I should stop thinking so much and start building?

The propane burner is easier to handle I think. But it gets a bit expensive over time. At least with the prices here.

Do you coat the inside of you steel "melting pot"(the word escapes me atm) with anything?

Yes, I do cover the crucible with something I don't know the English word for. Steel crucibles won't last forever. Al dissolves in steel, so it is eating it from the inside. And on the outside, it corrodes from the heat. But they are easy to handle (with the two hooks you can see on my video).

Nick

Dear Tea Lady, I was not far from you when I was casting. The factory was behind Fountain Gate in Lower Gully. I don,t cast any more but I am will to advise about foundry's. of the backyard type. The furnace lining that I forgot the name of is Kao Wool. I had a cast-able refractory base in a drum the size was about 2.6 inches high by about 2 ft in Dia. The Kao Wool was wrapped around the inside of the drum and was about 1 inch thick.. I think it was wound around twice. You could touch the outside of the drum even after three melts. The lid was the top of the drum lined with Kao Wool and had a 4 inch dia hole in the middle. Heat was LPG I got mine from the local servo. This was put in at the bottom of the furnace on an angle to create the swirling of the heat around then crucible. The method was a large gas-air torch. When I first started the furnace was located in Richmond inner Melbourne and did not make much noise in fact the Vac was the nosiest piece,
Now fior the crunch. The furnace is the easy part it is the re working of the sand which is the drama. In green sand moulding The sand has to be mulled to restore it to a useable state. After use it is dry and the muller squeezes the sand and get rid of all the lumps. Some Bentonite is added this is clay which binds the sand together. Finally water is added. If I remember it is about 3 or 4 percent. More than this and the sand is too wet and results in a volcanic effect from the steam created.
So if you are going to play in the foundry the sand is the drama.
But as I have said I will give all the advice necessary
Yours 4--6-4.

Originally Posted by 4-6-4

Dear Tea Lady, ......
So if you are going to play in the foundry the sand is the drama.
But as I have said I will give all the advice necessary
Yours 4--6-4.

I have built pottery kilns and mucked about with clay and glazes for 25 years. Metal just kind of intrigues me. I wonder if it is something you could do in a raku kiln? Probably. One day. In my spare time.

G,day Nick, I have watched the vid again and I liked the rapping tool. I would like to have a closer look at the muller. Does the rollers in it rise and fall. and lastly what was the mould with the cores in it. I liked the method of pouring with the lug on the bottom . I used graphite crucibles and lifted them a large pair of tongs on to a firebrick pedestal and then a ring to pour. Is the sand you use green sand or an oil based sand. Yours 4-6-4

Nick,

Yes, I do cover the crucible with something I don't know the English word for. Steel crucibles won't last forever. Al dissolves in steel, so it is eating it from the inside. And on the outside, it corrodes from the heat.

what's the German word for your coating of the steel crucible? I might know the English word for it - and I'd like to know too
Joe

what's the German word for your coating of the steel crucible?

It is "Tiegelschlichte" or "Pfannenschlichte".


The muller's wheels do move up and down (by own weight).
The casting with the core is an A-frame of a diesel engine (scale 1:10). It didn't work this time. But for sure the next time.
I also have those plier for and a ring for carbon crucibles.
The sand I'm using is oil-bound sand. I'm buying it ready-made and then regenerate it in that muller. I'm slowly getting better at that art.

The sand-rammer, I got for 25 Euros off fleeBay.


Nick

Ah, thanks Nick.
The English equivalent is 'Crucible wash' and 'ladle wash' sometimes called crucible or ladle 'slip'.
This is one brand: http://www.refractories.com/pdf_prod...DLE%20WASH.pdf
What do you use?
Cheers,
Joe

The English equivalent is 'Crucible wash'

Ah, now I remeber that I have forgotten that word.
I don't know what brand I have. I got it from my secret agent, my mystery source.


Nick

Dear Nick, Thanks for the info. We have an oil based sand in Melbourne called Petro Bond. I had small quantities and used it as a facing sand backed up with green sand. I know some small foundries used it exclusively. The muller I had was 1.2 meters and the bowl was falling to bits but it worked. I loaded drums of sand into it with an electric hoist. Did you build yours. Our full time foundries are getting thin on the ground and only use chemically bonded sands. They also do not like the small one offs. Please do another vid the next time you cast. Yours 4-6-4

One of my books calls it a "refactory wash"

My thinking behind preheating is that it would increase the flame temp so things would get hotter faster. I'm not sure this is strictly correct.

Stuart